Study on dielectrics and low-temperature viscosity performance of high-frequency difluorovinyl liquid crystals

With the rapid development of switchable devices for the K-band (≤40GHz) frequency range, there is a strong demand for liquid crystals (LCs) exhibiting high birefringence, low melting point and low dielectric loss ,low viscosity and good miscibility. The novel series of difluorovinyl liquid crystal compounds with Δn value around 0.4, relatively low melting point which can be as low as 34.4℃ were designed and synthesized. Comparing the difluorovinyl liquid crystal compound with isothiocyanide-containing liquid crystals, UV absorption test and dielectric loss test analysis at high frequency were performed. Difluorovinyl liquid crystals were prepared into a mixed liquid crystal material for high-frequency dielectric loss test and viscosity performance test analysis at different temperatures to explore its low temperature viscosity dependenceon temperature. The experimental results show that the difluorovinyl liquid crystal compounds not only have higher Δn value and lower melting point, but also have lower dielectric loss at high frequency and low temperature viscosity, which can improve the low temperature viscosity performance of liquid crystal materials.